First clathrochelate iron and cobalt(II) tris-dioximates with reactive apical substituents

Article abstract of DOI:10.1016/j.inoche.2013.01.020

Direct template macrobicyclization of three 1,2-cyclohexanedione dioxime molecules with monofunctionalized HO-, H₂N- and HOOC-containing phenylboronic acids on Fe^{2 +} and Co^{2 +} ions as a matrix afforded new macrobicyclic iron and cobalt(II) tris-dioximates with reactive apical substituents. The clathrochelates synthesized has been characterized by spectroscopic methods, X-ray crystallography and cyclic voltammetry.

Full text of DOI:10.1016/j.inoche.2013.01.020

Inorganic Chemistry Communications 30 (2013) 53–57
Contents lists available at SciVerse ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
First clathrochelate iron and cobalt(II) tris-dioximates with reactive
apical substituents
Ekaterina G. Lebed a, Alexander S. Belov a, Alexander V. Dolganov a, Anna V. Vologzhanina a,
Agnieszka Szebesczyk b, Elzbieta Gumienna-Kontecka b, Henryk Kozlowski b, Yurii N. Bubnov a,
Igor Y. Dubey c, Yan Z. Voloshin a,
⁎
a
Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences, 28 Vavilova str., 119991 Moscow, Russia
University of Wroclaw, Faculty of Chemistry, 14 F. Joliot-Curie str., 50-383 Wroclaw, Poland
Institute of Molecular Biology and Genetics NASU, 50, Acad. Zabolotnoho St., 03680 Kiev, Ukraine
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Direct template macrobicyclization of three 1,2-cyclohexanedione dioxime molecules with monofunctionalized
HO-, H2N- and HOOC-containing phenylboronic acids on Fe2+ and Co2+ ions as a matrix afforded new
macrobicyclic iron and cobalt(II) tris-dioximates with reactive apical substituents. The clathrochelates synthe-
sized has been characterized by spectroscopic methods, X-ray crystallography and cyclic voltammetry.
© 2013 Elsevier B.V. All rights reserved.
Received 5 December 2012
Accepted 23 January 2013
Available online 31 January 2013
Keywords:
Macrocyclic compounds
Clathrochelates
Iron complexes
Cobalt complexes
Ligand reactivity
Cage complexes with encapsulated metal ions (clathrochelates)
having high chemical stability and unique physical and physicochemi-
cal properties [1] have been widely used as suitable molecular scaffolds
and building blocks for the design of materials that meet the criteria for
practical use [2–18]. In particular, their functionalization with
closo-borate-containing ribbed substituents gave some prospective tar-
get compounds for boron-neutron capture therapy of cancer [19–21],
and that with halogen atoms and thiol-terminated spacer groups
afforded very efficient electrocatalysts (including those immobilized
on a surface of a working electrode) for hydrogen production [22,23].
Moreover, several clathrochelate iron(II) tris-dioximates have also
been tested as transcription inhibitors in the systems of model enzymes
(RNA and DNA polymerases, topoisomerase, etc.) and were found [24]
to be very efficient inhibitors in the case of T7 RNA polymerase; so
they are prospective antiviral and antitumor drug candidates.
The presence of reactive terminal groups in the apical capping
fragments of clathrochelates allows varying their properties: these
groups help to perform further modification and functionalization of
clathrochelates (in particular, for chemical immobilization of the
clathrochelate-based electrocatalysts on a surface of element oxide ma-
trices or metallic working electrodes [23]). Thus, protono- and ionogenic
groups increase their solubility in water and other biological media for
biological studies [25]. Reactive and donor groups can be used to modu-
late the biological activity of functionalized cage metal complexes using
pharmacophore or bio-relevant substituents, in particular, organic cat-
ionic, N-donor heterocyclic (including nucleotides), aromatic intercalat-
ing and oligopeptide residues. The choice of these groups can be made by
using preliminary molecular docking calculations (starting from experi-
mental X-ray and NMR data) optimizing their hydrophobic–hydrophilic
balance.
Among the tris-dioximate d-metal clathrochelates, the complexes
of the alicyclic 1,2-cyclohexanedion dioxime (nioxime, H2Nx) are the
most stable, and much easier to synthesize than the similar acyclic
compounds due to the fact that nioxime has a cis-conformation
both in crystal and in solution [1]. In this paper, we describe the syn-
thesis, structure, and spectral and electrochemical properties of first
tris-dioximate iron and cobalt(II) clathrochelates with reactive apical
hydroxyl, carboxyl and amino groups. They were obtained in moder-
ate yields by template condensation of nioxime with HO-, H2N-
and HOOC-monofunctionalized phenylboronic acids on a corre-
sponding metal ion as a matrix (Scheme 1) [26]. In the case of
3-aminophenylboronic acid, triethylamine as a strong organic base
was added to prevent the protonation of terminal amino groups by
H+ ions formed in the reaction course.
The complexes synthesized were characterized using elemental
analysis, MALDI-TOF and ESI mass spectrometry, IR, UV–vis, EPR (in
the case of the cobalt(II) complexes), 1H, 11B and 13C{1H} NMR
⁎
Corresponding author. Tel.: +7 4991359344; fax: +7 4991355085.
E-mail address: voloshin@ineos.ac.ru (Y.Z. Voloshin).
1387-7003/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.inoche.2013.01.020

54
E.G. Lebed et al. / Inorganic Chemistry Communications 30 (2013) 53–57
Scheme 1. Template synthesis of the apically functionalized iron and cobalt(II) clathrochelate tris-dioximates.
spectroscopies and X-ray crystallography (in the case of para-
hydroxymethylphenylboron-capped iron(II) clathrochelate); their elec-
trochemical properties were studied by cyclic voltammetry (CV).
The number and the position of signals in 1H and 13C{1H} NMR
spectra of the iron and cobalt(II) clathrochelates synthesized,
together with the ratios of their integral intensities in the 1H NMR
spectra confirmed the composition of their macrobicyclic molecules
as well as their C3-symmetry. In the case of the cobalt(II) complexes,
the paramagnetic broadening has prevented an observation of the
signals of the carbon nuclei being in close proximity to the encapsu-
lated paramagnetic metal ion.
forms the strong hydrogen bonds O7\H7W⋯O8 and O8\H8W⋯O5
with ri (O⋯O)=2.801(3) and 2.967(3) Å and the O\H\O angles equal
to 176 and 174°, respectively. As a result, in this crystal the infinite
H-bonded chains of the clathrochelate molecules are observed (Fig. 2).
Glassy EPR spectra of these cobalt complexes at 60 K (see SM, Fig. S1)
are characteristic of the low-spin cobalt(II) clathrochelates with Jahn–
Teller distortion [15]. Both g- and hyperfine tensors are rhombic, and
the spectra contain well-resolved eight-line splittings in the downfield re-
gion caused by hyperfine interactions with the 59Co nucleus (ICo =7/2).
The positive range of ESI mass-spectra for most of the iron(II) com-
plexes contains three intensive peaks assigned to their ionic associates
with Н+, Na+ and K+ cations. In the spectrum of the cobalt(II)
clathrochelate CoNx3(B(meta-C6H4COOH))2, the peak of the molecular
ion [M]+• is the most intensive. The spectra of other clathrochelates syn-
thesized also contain the peaks assigned to the cationic species that
resulted from the detachment of either one apical substituent at the cap-
ping boron atom (for the FeNx3(B(meta-C6H4NH2))2 complex), or one
apical capping moiety with the formation of semiclathrochelate species
(for the clathrochelates CoNx3(B(meta-C6H4COOH))2 and FeNx3(-
B(para-C6H4OH))2). For all these species, the experimental isotopic dis-
tribution is in a good agreement with the calculated model. In the
negative range of these spectra no peaks of any anionic macrobicycles
or their derivatives were found.
The X-ray molecular structure of the clathrochelate FeNx3(B(para-C6-
H4CH2OH))2 is shown in Fig. 1; its main geometrical parameters are
listed in Table S1 (see SM) together with the data for some other
macrobicyclic tris-nioximates. The geometry of its FeN6-coordination
polyhedron is intermediate between a trigonal prism (the distortion
angle φ=0°) and a trigonal antiprism (φ=60°), and the averaged φ
value (approximately 21.0°) is characteristic of the boron-capped
iron(II) tris-nioximates. The rigidity of the N_C\C_N chelate frag-
ments (with deviation angles ranging from 6 to 9°) causes the bite
angle α (half of the chelate N\Fe\N angle) and the heights h of their co-
ordination polyhedra (39° and 2.35 Å, respectively) to persist. The aver-
age Fe\N distance (approximately 1.905 Å) is also characteristic for
these iron(II) clathrochelate (Table S1); an encapsulated iron(II) ion is
situated in the center of the coordination polyhedron, so all the Fe\N
bond lengths are almost equal except for the elongated Fe(1)\N(5)
bond (1.918(2) Å) with the α-dioximate chelate ribbed fragment that
Fig. 1. General view of the clathrochelate FeNx3(B(para-C6H4CH2OH))2. Hydrogen
atoms except for those of the OH groups are omitted for clarity.

E.G. Lebed et al. / Inorganic Chemistry Communications 30 (2013) 53–57
55
Fig. 2. Fragment of the H-bonded chain in a crystal FeNx3(B(para-C6H4CH2OH))2·CH2Cl2. Hydrogen bonds are depicted with dashed line, H(C) atoms and solvate molecules are
omitted for clarity.
Besides, a donation of the electron density to the O(5) atoms of the
clathrochelate framework through these hydrogen bonds can be the rea-
son for the elongation of the corresponding B\O, N\O and Fe\N bonds.
Indeed, the B(1)\O(5), N(5)\O(5) and Fe(1)\N(5) distances
(1.524(3), 1.389(3) and 1.918(2) Å, respectively) are the largest
among the X-rayed boron-capped iron(II) tris-nioximates (Table S1).
The obtained UV–vis spectra of the iron(II) clathrochelates contain in
the visible region two metal-to-ligand charge transfer (MLCT) bands,
Fed→Lπ*, characteristic of the macrobicyclic iron(II) tris-dioximates;
first at approximately 430 nm (e ~3 – 6·103 L mol–1 cm–1), and second
at around 460 nm (e ~1–2·104 L mol–1 сm–1). These CT bands for
iron(II) complexes are four times more intensive and substantially (by
approximately 30 nm) shortwave-shifted as compared with those for
the corresponding cobalt(II) macrobicycles. Besides the CT bands caused
by the transitions in the same tris-nioximate macrobicyclic frameworks,
the spectra are very similar in the visible range. In the UV range the
bands of the π−π* transitions in their apical aromatic substituents, in ad-
dition to those of the same nature in the chelate α-dioximate fragments
of the macrobicyclic polyene ligands, are observed. The electrochemical
characteristics of the iron and cobalt(II) complexes obtained were stud-
ied by CV. As it follows from the linear plot Ip versus v1/2 (where v is scan
rate), all waves in their CVs are characteristic for the current
diffusion-controlled processes in steady-state conditions; the oxidation
and reduction potentials are listed in Table S2 (see SM). These CVs have
similar shapes (Fig. 3) and contain one cathodic reduction wave and
one anodic oxidation wave. The one-electron wave in the anodic
range was assigned to the metal-centered M2+/3+ redox processes,
and its potential only slightly depends on the nature of the
functionalizing reactive groups (Table S2). This effect comes from
their large distance from the redox-active encapsulated metallocenter.
In the cathodic ranges, the quasi-reversible M2+/+ waves domi-
nate. The ratio between the peaks for the direct and backward pro-
cesses for the iron clathrochelates is much less than 1, indicating
the formation of their chemically unstable anionic iron(I)-containing
species which easily undergo further decomposition reactions.
The values of the redox potentials (Table S2) allow estimating a
difference between the frontier orbitals of these complexes using the
magnitudes of their “electrochemical gap” (ΔE=Eox −Ered). Low ΔE
values are characteristic for the complexes with the redox-processes
localized on close-in-energy frontier orbitals. All the macrobicyclic
cobalt(II) tris-nioximates obtained have the same electronic structures
and, therefore similar electrochemical behavior with characteristic
low ΔE values close to each other. In the case of their iron(II)-containing
analogs, these values are substantially higher.
The difference observed in redox properties of the iron and cobalt(II)
complexes with the same macrobicyclic ligands can be explained
mainly by their different electronic configurations (d6 and d7, respec-
tively) and, therefore, different chemical stability of the corresponding
reduced (oxidized) anionic (cationic) clathrochelate forms. In particu-
lar, the aliphatic cobalt clathrochelates are stable in two oxidation states
of an encapsulated cobalt ion (+2 and +3), whereas their iron-
containing analogs undergo the side chemical reactions.
Therefore, we synthesized and characterized new apically func-
tionalized macrobicyclic iron and cobalt(II) tris-dioximates with
terminal reactive groups to allow their use as clathrochelate precur-
sors and “building blocks” for the design of both the polytopic and
Fig. 3. CV for 1 mM DMF solution of the clathrochelate. CoNx3(B(meta-C6H4NH2))2 on
platinum electrode at a scan rate 200 mV s−1
.

56
E.G. Lebed et al. / Inorganic Chemistry Communications 30 (2013) 53–57
[25] I.G. Belaya, G.E. Zelinskii, A.S. Belov, O.A. Varzatskii, V.V. Novikov, A.V. Dolganov,
H. Kozlowski, Ł. Szyrwiel, Y.N. Bubnov, Y.Z. Voloshin, Polyhedron 40 (2012) 32.
[26] Synthesis. FeNx3(B(para-C6H4COOH))2. FeCl2·4H2O (0.06 g, 0.29 mmol) and
nioxime (0.14 g, 0.99 mmol) were dissolved/suspended in methanol (5 ml) and
a solution of para-carboxyphenylboronic acid (0.11 g, 0.66 mmol) in methanol
(5 ml) was added dropwise to the stirring reaction mixture. The reaction mixture
was stirred for 4 h and left for 24 h. The dark-orange precipitate formed was fil-
tered off, washed with methanol (15 ml, in three portions), diethyl ether (15 ml,
in three portions), and hexane (15 ml, in three portions), and dried in vacuo.
Yield: 0.13 g (60%). Anal. Calc. for C32H34N6O10B2Fe (%): C, 51.90; H, 4.59; N,
multicentered hybrid systems and efficient transcription inhibitors
(the iron macrobicycles) as well as immobilized clathrochelate-based
electrocatalysts for hydrogen production (the cobalt complexes).
Acknowledgments
The authors gratefully acknowledge the support of the RFBR (grants
11-03-12181, 12-03-00955 and 12-03-00961), SFFR of Ukraine (grant
F40.4/078), the Marie Curie IIF Scheme of the 7th EU Framework Pro-
gram (grant 295160), and Council of the President of the Russian Feder-
ation (program of state support of leading scientific schools, grant NSh
5943.2012.3). The authors also thank Dr. V. Novikov for the NMR and
EPR measurements.
11.35. Found (%): C, 51.71; H, 4.46; N, 11.21. MS (MALDI-TOF) m/z (I, %): 740
+
(100) [M]+•, 763 (10) [M+Na+
]
.
1H NMR (DMSO-d6): δ, ppm: 1.74 (s, 12H,
β-CH2), 2.84 (s, 12H, α-CH2), 7.69 (m, 4H, meta-Ph), 7.88 (m, 4H, ortho-Ph),
12.78 (s, 2H, OH). 13C{1H} NMR (DMSO-d6): δ, ppm: 21.25 (s, β-CH2), 26.33 (s,
α-CH2), 128.50 (s, meta-Ph), 130.33 (s, para-Ph), 132.06 (s, ortho-Ph), 152.82
(s, C_N), 168.24 (s, C_O). IR (KBr) ν/cm−1: 964, 1062, 1125 ν(N\O), 1202m
ν(B\O), 1578 ν(C_N), 1686 ν(C_O). UV–vis (DMSO):
λ ,
max/nm (ε·10−3
mol−1 l cm−1): 281 (14), 302 (4.1), 357 (2.5), 430 (4.1), 455 (15). FeNx3(-
B(para-C6H4CH2OH))2. FeCl2·4H2O (0.065 g, 0.33 mmol), nioxime (0.15 g,
1.08 mmol) and para-(hydroxymethyl)phenylboronic acid (0.11 g, 0.72 mmol)
were dissolved/suspended in methanol (10 ml). The reaction mixture was stirred
for 4 h and left for 24 h. The precipitate formed was filtered off, washed with
methanol (15 ml, in three portions) and dried in air. The product was extracted
with chloroform (15 ml), the extract was filtered, evaporated to a small volume
and precipitated with hexane. The precipitate was filtered off, washed with hex-
ane and dried in vacuo. Yield: 0.19 g (82%). Anal. Calc. for C32H38N6O8B2Fe (%): C,
53.83; H, 5.34; N, 11.80; Fe, 7.86. Found (%): C, 53.13; H, 5.16; N, 11.71; Fe, 8.00.
Appendix A. Supplementary data
The details of X-ray diffraction, analytical and spectral data collections,
the corresponding spectra and tables are given in the Supplementary
material.
CCDC 912550 contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge via http://www.
ccdc.cam.ac.uk/conts/retrieving.html. Supplementary data related to
this article can be found online at http://dx.doi.org/10.1016/j.inoche.
2013.01.020.
MS (MALDI-TOF) m/z (I, %): 712 (100) [M]+•, 725 (22) [M+Na+
]
+, 751(10)
+
+
[M+K+
]
+. MS (ESI) m/z (I, %): 713 [M+H+
]
(100), 735 [M+Na+
]
(30),
751 [M+K+
]
(20). 1H NMR (CDCl3): δ, ppm: 1.82 (s, 12H, β-CH2 (Nx)), 2.96
+
(s, 12H, α-CH2(Nx)), 3.55 (s, 2H, OH), 4.76 (s, 4H, CH2(CH2OH)), 7.39 (m, 4H,
meta-Ph), 7.74 (m, 4H, ortho-Ph). 13C{1H} NMR (CDCl3): δ, ppm: 21.63 (s,
β-CH2(Nx)), 26.31 (s, α-CH2(Nx)), 66.01 (s, CH2OH), 126.32 (s, meta-Ph),
132.01 (s, ortho-Ph), 140.30 (s, para-Ph), 151.86 (s, C_N). IR (KBr) ν/cm−1
:
938, 961, 1061 ν(N\O), 1202m ν(B\O), 1579 ν(C_N). UV–vis (CH2Cl2): λ-
max/nm (ε·10−3, mol−1 l cm−1): 255 (5.7), 281 (8.9), 292 (5.1), 357 (1.4), 441
(14), 458 (5.1). FeNx3(B(para-C6H4OH))2. FeCl2·4H2O (0.066 g, 0.33 mmol),
nioxime (0.155 g, 1.09 mmol) and para-hydroxyphenylboronic acid (0.1 g,
0.72 mmol) were dissolved/suspended in methanol (5 ml) and the reaction mix-
ture was stirred for 4 h. The precipitate formed was filtered off, washed with
methanol (20 ml, in four portions), diethyl ether, hexane and dried in vacuo.
Yield: 0.19 g (83%). Anal. Calc. for C30H34N6O8B2Fe (%): C, 52.63; H, 4.97; N,
12.28. Found (%): C, 52.48; H, 4.95; N, 12.14. MS (MALDI-TOF) m/z (I, %): 684
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(100) [M]+•, 707 (10) [M+Na+
]
,
+, 723 (3) [M+K+
]
+. MS (ESI) m/z (I, %): 580
(10) [M−HOC6H4B2++3H+
]
609 (15) [M−HOC6H4−+HO−+H+
]
,
685
+
+
(70) [M+H+
]
+, 707 (100) [M+Na+
]
.
1H NMR (DMSO-d6): δ, ppm: 1.72 (s,
+
12H, β-CH2), 2.80 (s, 12H, α-CH2), 6.69 (m, 4H, meta-Ph), 7.36 (m, 4H,
ortho-Ph), 9.13 (s, 2H, OH). 13C{1H} NMR (DMSO-d6): δ, ppm: 21.33 (s, β-CH2),
26.28 (s, α-CH2), 114.55 (s, meta-Ph), 131.35 (s, para-Ph), 133.18 (s, ortho-Ph),
151.99 (s, C_N), 157.36 (s, COH). IR (KBr) ν/cm−1: 961, 1057, 1174, 1199
ν(N\O), 1227m ν(B\O), 1580 ν(C_N). UV–vis (CH2Cl2): λmax/nm (ε·10−3
,
mol−1 l cm−1): 252 (5.3), 279 (4.6), 286 (7.4), 345 (2.3), 426 (2.6), 453 (13).
FeNx3(B(meta-C6H4NH2))2. FeCl2·4H2O (0.07 g, 0.36 mmol), nioxime (0.17 g,
1.2 mmol) and meta-aminophenylboronic acid (0.12 g, 0.8 mmol) were
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dissolved/suspended in methanol (5 ml) and
a solution of triethylamine
(0.1 ml, 0.72 mmol) in methanol (5 ml) was added dropwise to the stirring reac-
tion mixture. The reaction mixture was left for 24 h and then the precipitate
formed was filtered off, washed with methanol (15 ml, in three portions) and
dried in air. The solid was extracted with chloroform (15 ml) and the extract
was flash chromatographed through a silica gel (30-mm layer, eluent: chloro-
form–acetonitrile 2:1). The elute was evaporated to a small volume and precipi-
tated with hexane. The precipitate was filtered off, washed with hexane and dried
in vacuo. Yield: 0.19 g (77%). Anal. Calc. for C30H44N8O6B2Fe (%): C, 52.79; H,
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5.28; N, 16.42; Fe, 8.21. Found (%): C, 52.26; H, 5.16; N, 16.27; Fe, 8.10. MS
+
(MALDI-TOF) m/z (I, %): 682 (100) [M]+•
,
705 (12) [M+Na+
]
,
721(25)
+
+
[M+K+
]
.
MS (ESI) m/z (I, %): 590 (25) [M−H2NC6H4−
]
,
683 (100)
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Novikov, Y.N. Bubnov, Inorg. Chim. Acta 370 (2011) 322.
[M+H+
] .
1H NMR (DMSO-d6): δ, ppm: 1.74 (s), 12H, β-CH2, 2.82 (s, 12H,
+
α-CH2), 4.76 (s, 4H, NH2), 6.48 (m, 2H, Ph), 6.78 (m, 2H, Ph), 6.83 (m, 2H, Ph),
6.93 (m, 2H, ortho-Ph). 13C{1H} NMR (DMSO-d6): δ, ppm: 21.33 (s, β-CH2),
26.31 (s, α-CH2), 113.8, 118.38, 120.12, 127.90 (all s, Ph), 147.63 (s, C\NH2),
151.99 (s, C_N). IR (KBr) ν/cm−1: 938, 992, 1060, ν(N\O), 1188m ν(B\O),
1579 ν(C_N). UV–vis (CH2Cl2): λmax/nm (ε·10−3, mol−1 l cm−1): 238 (24),
278 (11), 298 (5.7), 327 (2.6), 367 (1.1), 440 (11), 457 (5.3). FeNx3(B(meta-C6-
H4COOH))2. FeCl2·4H2O (0.65 g, 3.26 mmol), nioxime (1.62 g, 11.4 mmol) and
meta-carboxyphenylboronic acid (1.35 g, 8.1 mmol) were dissolved/suspended
in methanol (30 ml) and the reaction mixture was stirred for 3 h. The precipitate
formed was filtered off, washed with methanol (15 ml, in three portions), diethyl
ether (15 ml, in three portions) and hexane (15 ml, in three portions), and dried
in vacuo. Yield: 2.20 g (90%). Anal. Calc. for C32H34N6O10B2Fe (%): C, 51.90; H,
4.59; N, 11.35; Fe, 7.57. Found (%): C, 51.70; H, 4.55; N, 11.22; Fe, 7.70. MS
[16] Y.Z. Voloshin, I.G. Belaya, A.S. Belov, V.E. Platonov, A.M. Maksimov, A.V.
Vologzhanina, Z.A. Starikova, A.V. Dolganov, V.V. Novikov, Y.N. Bubnov, Dalton
Trans. 41 (2012) 737.
[17] A.S. Belov, A.I. Prikhod'ko, V.V. Novikov, A.V. Vologzhanina, Y.N. Bubnov, Y.Z.
Voloshin, Eur. J. Inorg. Chem. (2012) 4507.
[18] Y.Z. Voloshin, A.S. Belov, O.A. Varzatskii, S.V. Shul'ga, P.A. Stuzhin, Z.A. Starikova,
E.G. Lebed, Y.N. Bubnov, Dalton Trans. 41 (2012) 921.
[19] Y.Z. Voloshin, O.A. Varzatskii, K.Y. Zhizhin, N.T. Kuznetsov, Y.N. Bubnov, Russ.
Chem. Bull. 55 (2006) 22.
[20] Y.Z. Voloshin, O.A. Varzatskii, Y.N. Bubnov, Russ. Chem. Bull. 56 (2007) 577.
[21] N.T. Kuznetsov, I.G. Belaya, A.V. Dolganov, G.E. Zelinsky, E.Y. Matveev, K.Y.
Zhizhin, Y.Z. Voloshin, Y.N. Bubnov, Russ. Chem. Bull. 60 (2011) 2469.
[22] Y.Z. Voloshin, A.V. Dolganov, O.A. Varzatskii, Y.N. Bubnov, Chem. Commun. 47
(2011) 7737.
[23] Y.Z. Voloshin, A.S. Belov, A.V. Vologzhanina, G.G. Aleksandrov, A.V. Dolganov, V.V.
Novikov, O.A. Varzatskii, Y.N. Bubnov, Dalton Trans. 41 (2012) 6078.
[24] Y. Voloshin, O. Varzatskii, S. Shul'ga, V. Novikov, A. Belov, I. Makarenko, I. Dubey,
D. Krivorotenko, V. Negrutska, K. Zhizhin, N. Kuznetsov, Y. Bubnov, Proc. 10th
EUROBIC, Thessaloniki, Greece, 22–26 June, 2010, 2010, p. 29.
+
+
(ESI) m/z (I, %): 741 (100) [M+H+
] , ] , 779 (10)
763 (10) [M+Na+
+
[M+K+
]
.
1H NMR (DMSO-d6): δ, ppm: 1.75 (s, 12H, β-CH2), 2.85 (s, 12H,
α-CH2), 7.43 (m, 2H, meta-Ph), 7.79 (m, 2H, Ph), 7.87 (m, 2H, Ph), 8.18 (s, 2H,
Ph), 12.75 (s, 2H, OH). 13C{1H} NMR (DMSO-d6): δ, ppm: 21.25 (s, β-CH2),
26.34 (s, α-CH2), 127.81, 129.11, 129.91, 132.97, 136.51 (all s, Ph), 152.78 (s,
C_N), 168.46 (s, C_O). IR (KBr) ν/cm−1: 947, 1000, 1062 ν(N\O), 1201m

E.G. Lebed et al. / Inorganic Chemistry Communications 30 (2013) 53–57
57
ν(B\O), 1581 ν(C_N), 1682 ν(C_O). UV–vis (DMSO):
λ
max/nm (ε·10−3 [M]+• 1H NMR (DMSO-d6): δ, ppm: −34.19 (s, 12H, α-CH2), 5.15 (s, 12H,
,
.
mol−1 l cm−1): 282 (16), 308 (1.7), 346 (1.5), 434 (5.9), 450 (15). CoNx3(-
B(para-C6H4COOH))2. CoCl2 (0.087 g, 0.67 mmol), nioxime (0.33 g, 2.4 mmol)
and para-carboxyphenylboronic acid (0.28 g, 1.7 mmol) were dissolved/
suspended in methanol (10 ml) under argon and the reaction mixture was
stirred for 4 h. The precipitate formed was filtered off, washed with methanol
(15 ml, in three portions) diethyl ether (15 ml, in three portions), and hexane
(15 ml, in three portions), and dried in vacuo. Yield: 0.43 g (87%). Anal. Calc.
for C32H34N6O10B2Co (%): C, 51.68; H, 4.58; N, 11.31; Co, 7.94. Found (%): C,
β-CH2), 6.86 (br s, 6H, Ph), 7.55 (br s, 2H, Ph), 12.50 (s, 2H, OH). 13C{1H} NMR
(DMSO-d6): δ, ppm: 127.69, 128.20, 129.73, 133.71, 137.31 (all s, Ph), 167.84
(s, C_O). IR (KBr) ν/cm−1: 943, 998, 1064 ν(N\O), 1203m ν(B\O), 1600
ν(C_N), 1685 ν(C_O). UV–vis (DMSO): λmax/nm (ε·10−3, mol−1 l cm−1):
270 (11), 305 (4.9), 361 (6.6), 436 (1.9), 477 (5.3). CoNx3(B(meta-C6H4NH2))2.
CoCl2 (0.056 g, 0.43 mmol), nioxime (0.215 g, 1.51 mmol) and meta-
aminophenylboronic acid (0.165 g, 1.07 mmol) were dissolved/suspended in
methanol (6 ml) under argon and the reaction was stirred for 10 min. Then a so-
lution of triethylamine (0.15 ml, 1.07 mmol) in methanol (5 ml) was added
dropwise to the stirring reaction mixture for 35 min. The reaction mixture was
stirred for 3 h and left for 24 h. The precipitate formed was filtered off, washed
with methanol (10 ml, in two portions) and dried in air. The solid was extracted
with chloroform and the extract was flash chromatographed through a silica gel
(30-mm layer, eluent: chloroform–acetonitrile 10:1). The elute was evaporated
to a small volume and precipitated with hexane. The precipitate was filtered
off, washed with hexane and dried in vacuo. Yield: 0.105 g (35%). Anal. Calc. for
51.57; H, 4.66; N, 11.14; Co, 8.10. MS (MALDI-TOF) m/z: 743 [M]+• 1H NMR
.
(DMSO-d6): δ, ppm: −34.40 (s, 12H, α-CH2), 5.15 (s, 12H, β-CH2), 6.48 (br s,
4H, Ph), 7.89 (br s, 4H, Ph), 12.56 (s, 2H, OH). 13C{1H} NMR (DMSO-d6): δ,
ppm: 20.44 (s, β-CH2), 128.37, 128.50, 129.65, 132.74, 134.49 (all s, Ph), 167.84
(s, C_O). IR (KBr) ν/cm−1: 961, 1064 ν(N\O), 1203m ν(B\O), 1560 ν(C_N),
1686 ν(C_O). UV–vis (DMSO): λmax/nm (ε·10−3, mol−1 l cm−1): 272 (11),
296 (5.4), 360 (5.3), 443 (1.4), 478 (3.8). CoNx3(B(meta-C6H4COOH))2. CoCl2
(0.087 g,
0.67 mmol),
nioxime
(0.33 g,
2.4 mmol)
and
meta-
carboxyphenylboronic acid (0.29 g, 1.7 mmol) were dissolved/suspended in
methanol (10 ml) under argon and the reaction mixture was stirred for 4 h.
The precipitate formed was filtered off, washed with methanol (15 ml, in three
portions), diethyl ether (15 ml, in three portions) and hexane (15 ml, in three
portions), and dried in vacuo. Yield: 0.39 g (78%). Anal. Calc. for C32H34N6O10B2Co
(%): C, 51.68; H, 4.58; N, 11.31; Co, 7.94. Found (%): C, 51.51; H, 4.68; N, 11.18; Co,
C
30H36N8O6B2Co (%): C, 52.55; H, 5.25; N, 16.35; Co, 8.61. Found (%): C, 52.39;
H, 5.14; N, 16.24; Co, 8.72. MS (MALDI-TOF) m/z: 685 [M]+• 1H NMR (CD2Cl2):
.
δ, ppm: −33.69 (br s, 12H, α-CH2), 3.16 (br s, 4H, NH2), 5.09 (s, 12H, β-CH2),
5.70 (br s, 4H, Ph), 6.21 (s, 2H, Ph), 6.43 (s, 2H, Ph). 13C{1H} NMR (CD2Cl2): δ,
ppm: 22.40 (s, β-CH2), 115.48 (s, Ph), 120.81 (s, Ph), 124.21 (s, Ph), 129.97 (s,
Ph), 147.48 (s, C(NH2)). UV–vis (CH2Cl2): λmax/nm (ε·10−3, mol−1 l cm−1):
295 (8.0), 268 (4.2), 360 (4.0), 455 (1.4), 478 (3.0).
7.90. MS (ESI) m/z (I, %): 613 (20) [M−HOOCC6H4B2++3H+
]
+, 743 (100)
]
+. MS (MALDI-TOF) m/z: 743
[M]+•, 766 (10) [M+Na+ +, 782 (10) [M+K+
]